MC-17b motor innards and a question

[Bill Hunt]

I thought I’d better start a new thread with this, as it’s tangential to the thread it was originally added to:

I believe this is an MC-17b motor. I bought it without cables or other accessories in as-is condition.

Getting it to run was not difficult, but it was showing signs of corrosion on the fixing bolts so I thought I’d have a peek inside.

After dismantling and cleaning I set out to discover how it was meant to work—particularly the “friction drive” mechanism I’d seen mentioned in several related online texts.

What I’d originally thought was a clutch/friction mechanism (photo centre) turned out to be something more like a shock absorber made up of several wavy washers and tensioner rings, all pinned to the main gear—which was initially seized onto the outer shaft by corrosion.

I’ve studied the manual (which by the way states the motor runs on ball bearings—there are none), and I’m still no closer to understanding what constitutes the friction drive, and how it’s supposed to work.

The manual describes mechanical operation:

Pressing the motor lever fully home when the motor is not connected to the camera results in the motor running continuously with the drive shaft engaged.

When connected to the camera this would mean the camera drive shaft would also be rotating continuously.

Is this what’s meant to happen?

With the drive motor attached and running, and the camera lever at the “O” position (motor disengaged), is the camera in effect “idling” until the front or side shutter release is engaged?

Is this also why the manual advises the motor should not be left on in this state for more than 15minutes (wear on the camera mechanism)?

Thank you for reading this far, I’m aware that my assumptions may all be incorrect, in which case I’m happy to be corrected.

 

 

 

 

[Don H Marks]

If yours is not free to spin with friction it is still seized. 

Edited January 5 by Don H Marks

[Bill Hunt]

1 hour ago, Don H Marks said:

If yours is not free to spin with friction it is still seized. 

Hi Don and thank you,

I was just about to update… this is has become quite a puzzle.

I can assure you the gear is free to spin (and this I think is the key to the puzzle), as long as I remove the pin that secured the tension ring, springs and gear together.

What initially had me stumped was the pin looked like it was meant to be there—it may have been done at the factory by special order.

Interestingly enough, when I removed the pin earlier today I noticed it looks very much like the pin that goes through the camera drive shaft, with one end cut off.

With the pin removed, the clutch assembly is free to slip depending on the tension applied by the adjustment ring.

Getting the tension set correctly will at this point be a case of trial and error—unless anyone has some tips.

The main thing is (subject to the possibility of me being completely wrong in all my previous assumptions) the gearbox and friction clutch are able to do what they were designed to do.

 

[Simon Wyss]

I think this is another testimony of the many changes that were made at Paillard. When you study the service manual you see that it’s full of little things differing here and there over time. Regarding these motors I’m under the impression that out of experience somebody said the clutch or shock absorber, which it isn’t because the motor doesn’t start up like a synchronous machine, is unnecessary. We’ll make the thing straight, give it a bore here, place in a grooved pin. The argument was perhaps that the camera mechanism starts up even quicker when driven by spring force. On the other hand, to keep the electric motor turning with the camera at halt is something that only puzzles me. Maybe to produce warmth in the cold? In cold conditions I rather rely on the mainspring than a battery.

For a setting of the protective clutch you need to know the shear strength of the composite gear’s toothing. Then you give it a torque about a third lower. That’s how I’d do it.

[Bill Hunt]

42 minutes ago, Simon Wyss said:

I think this is another testimony of the many changes that were made at Paillard. When you study the service manual you see that it’s full of little things differing here and there over time. Regarding these motors I’m under the impression that out of experience somebody said the clutch or shock absorber, which it isn’t because the motor doesn’t start up like a synchronous machine, is unnecessary. We’ll make the thing straight, give it a bore here, place in a grooved pin. The argument was perhaps that the camera mechanism starts up even quicker when driven by spring force. On the other hand, to keep the electric motor turning with the camera at halt is something that only puzzles me. Maybe to produce warmth in the cold? In cold conditions I rather rely on the mainspring than a battery.

For a setting of the protective clutch you need to know the shear strength of the composite gear’s toothing. Then you give it a torque about a third lower. That’s how I’d do it.

Thank you Simon,

Your knowledge is invaluable.

From what I can understand from the manual, keeping the motor running and using either the front or side mechanical release is the only way of avoiding exposing frames when the camera stops:

This is my preferred method of running the camera with the motor—with a cable on the side shutter release.

Once I get a new pin in the camera’s drive shaft I’ll do a bit more testing, taking it slowly until I feel confident it’s reliable, and not going to damage the camera. I know it shouldn’t, but I’m being extra cautious.

 

 

 

 

[Brian Drysdale]

I seem to recall starting the motor & camera with an external on/off switch.

[Simon Wyss]

You can’t damage the camera with the Unimotor, perhaps a roll pin in place of a solid dowel. When you let turn the motor on that one heats up. Sooner or later the motor or the clutch catches fire. 🔥 😜

It’s not professional to keep the electric motor running for the amateurish demand of not overexposed first frames. Again a clash caused by the coining Professional Amateur by Paillard, since 1936. But suum cuique, I can’t alter everybody’s expectations. What I can do is praise the Bell & Howell Filmo 70 models that afford a totally different technical approach. If we compare the H to the 70 we begin with the side finder. Bye-bye, Bolex!

[Bill Hunt]

44 minutes ago, Brian Drysdale said:

I seem to recall starting the motor & camera with an external on/off switch.

Yes, that’s the other way of starting/stopping, but according to this description…

…the shutter may be left open after a take whereas with the manual release the shutter is always left closed.

I’d be interested to hear your thoughts though Brian as you have the advantage of having used the motor.

Did you find it reliable?

[Bill Hunt]

3 minutes ago, Simon Wyss said:

You can’t damage the camera with the Unimotor, perhaps a roll pin in place of a solid dowel. When you let turn the motor on that one heats up. Sooner or later the motor or the clutch catches fire. 🔥 😜

It’s not professional to keep the electric motor running for the amateurish demand of not overexposed first frames. Again a clash caused by the coining Professional Amateur by Paillard, since 1936. But suum cuique, I can’t alter everybody’s expectations. What I can do is praise the Bell & Howell Filmo 70 models that afford a totally different technical approach. If we compare the H to the 70 we begin with the side finder. Bye-bye, Bolex!

I understand Simon, and I take you point about (my) expectations.

This is part of the process of my education which, at this point, is very much lacking in experience in terms of this camera.

[Simon Wyss]

I don’t mean you but many people who have less technical interest in H cameras. It’s just got to be BOLEX.

If I can confuse you, let me explain that the early models have the better claw mechanism, the laterally correct film guidance, a mainspring that can be rewound during runs, longer lens mount threads in the turret, and a shutter opening angle of 190 degrees. More camera than with all the younger models. Interestingly, an electric motor can be attached to them as well, it takes an additional LH fastening screw though and a different coupling bush.

[Brian Drysdale]

2 hours ago, Bill Hunt said:

Yes, that’s the other way of starting/stopping, but according to this description…

…the shutter may be left open after a take whereas with the manual release the shutter is always left closed.

I’d be interested to hear your thoughts though Brian as you have the advantage of having used the motor.

Did you find it reliable?

This was many years ago. The motor we used had been modified to provide a sync output for the 1/4 tape recorder, so was different to most examples. It used the Leevers Rich system, basically a 1000hz tone pulse for each frame, this had issues unrelated to the motor, the mini jack connection on the Tandberg recorder was unreliable, so having a sync signal was hit or miss.

The camera was fitted with a barney for sync sound, later I made a DIY blimp for it, which was pretty heavy. Also, wasteful of film because we used 100 ft loads, so there was a lot of small short ends.

As I mentioned earlier, we had issues with the camera itself, not the motor, which appeared to be pretty reliable, although it wasn't getting heavy duty use.

Edited January 5 by Brian Drysdale

[Bill Hunt]

2 hours ago, Simon Wyss said:

I don’t mean you but many people who have less technical interest in H cameras. It’s just got to be BOLEX.

If I can confuse you, let me explain that the early models have the better claw mechanism, the laterally correct film guidance, a mainspring that can be rewound during runs, longer lens mount threads in the turret, and a shutter opening angle of 190 degrees. More camera than with all the younger models. Interestingly, an electric motor can be attached to them as well, it takes an additional LH fastening screw though and a different coupling bush.

Too much information is never enough Simon, I’m very interested in the details.

Part of my interest in manual shutter release while using the motor is being able to lap dissolve or double expose while shooting longer takes without the loss of frames. The Rexofader is fine for shorter stuff, but the motor would be handy for the longer ones. Of course timing then becomes an issue, but I think I can manage that.

By the way, my camera is an early (perhaps the first) reflex model. It was serviced by Dom last year. I work quite slowly these days as my wife’s not been well the last few years, but I find that having to take my time allows greater opportunities for thinking, which in turn means less chance of breaking stuff.

Thanks again.

P.S. A couple of work in progress photos:

 

 

[Bill Hunt]

1 hour ago, Brian Drysdale said:

This was many years ago. The motor we used had been modified to provide a sync output for the 1/4 tape recorder, so was different to most examples. It used the Leevers Rich system, basically a 1000hz tone pulse for each frame, this had issues unrelated to the motor, the mini jack connection on the Tandberg recorder was unreliable, so having a sync signal was hit or miss.

The camera was fitted with a barney for sync sound, later I made a DIY blimp for it, which was pretty heavy. Also, wasteful of film because we used 100 ft loads, so there was a lot of small short ends.

As I mentioned earlier, we had issues with the camera itself, not the motor, which appeared to be pretty reliable, although it wasn't getting heavy duty use.

Hands-on experience is worth a truckload of manuals, thanks Brian.

While there is apparently a reliable sync motor now available, I’ve decided sync sound is a bridge too far for my current circumstances.

My Nagra deck sighs disconsolately as I write this…

I remember you talking about the camera issue, good to know the motor was reliable.

I can’t remember if I mentioned before but the serial number and features on my motor make me think it’s quite a late model one. It even has a little “Reverse” button and plugs for shutter release and reverse control.

Unfortunately no cables or anything else came with the motor, but it has been a blessing in a way as I’ve kept the wiring very simple (see photo elsewhere in this thread).

I have a bit of time to think about it all as my replacement pin for the (camera) drive shaft is in a postman’s bag… somewhere.

Someone should collect all of these Bolex stories and put them somewhere accessible.
 

 

[Simon Wyss]

From what I can read and see you have the second reflex model, that is with the variable shutter. I call these RX-2 because I start to count with 1 and the first or RX model doesn’t have a VS. REX-3 would be the first series with the big base, REX-4 those with the 1-1 shaft on the outside for the ESM, and REX-5 is the magazine model.

Yes, the motor is a late one with the rear hand knob plus reverse.

All the best to your wife and everybody filming.

[Bill Hunt]

35 minutes ago, Simon Wyss said:

From what I can read and see you have the second reflex model, that is with the variable shutter. I call these RX-2 because I start to count with 1 and the first or RX model doesn’t have a VS. REX-3 would be the first series with the big base, REX-4 those with the 1-1 shaft on the outside for the ESM, and REX-5 is the magazine model.

Yes, the motor is a late one with the rear hand knob plus reverse.

All the best to your wife and everybody filming.

It’s a REX 2 from this day forward Simon, and thank you.